1. Field of the Invention
The present invention relates to a method for separating blood components, for example, plasma, platelet and erythrocyte, from whole blood contained in a flexible container such as a blood bag or the like, and also to an apparatus and an associated attachment, which is contrived for use in the method referred to above.
2. Description of the Related Art
Recently, it has been recognized that whole blood transfusions cause undesired effects on a patient. Therefore, in view of alleviating certain physiological burdens, and suppressing the side effects due to immune reaction, such a mode of transfusion is widely applied today, wherein only the blood component or components which the patient requires is transfused into a blood circulatory system of the patient.
To obtain blood component preparations, it is necessary to fractionate the whole blood collected in a master blood bag (donor bag) into respective components by using a centrifugal separator, and to separate the components by transferring each component into an individual sub-bag from the master bag.
To meet this requirement, the prior art uses such a separator 71 as illustrated in FIG. 1, wherein the blood components in the master bag 73, i.e. an upper layer comprising plasma, and a middle layer otherwise called a buffy coat (comprised mainly of leukocytes, and partly of platelets, erythrocytes and plasma mixed therein) which have been centrifugally fractionated from the whole blood, are separately transferred into their sub-bags manually, and then sealed with a blockade provided in a connecting tube leading to each sub-bag, using a tube sealer.
More specifically, the master blood bag 73 which has been subjected to centrifugal separation is first set on suspender pins 75 of said separator, with care not to stir up the blood cells in said master blood bag.
FIG. 2A shows how the master blood bag is set in that position, wherein 77 denotes plasma, 79 a buffy coat, and 81 dense erythrocytes.
Next, the master blood bag 73 is held between a retainer plate 87 (FIG. 1) of the separator 71, and a pressurizing plate 89 which swings via a lever 83 to which certain force is applied constantly in a given direction from a spring (not shown), with the lever 83 of the separator 71 disengaged from the hook 85 held on a base 84, whereby a plasma component 77 constituting the upper layer may be transferred into a first sub-bag (not shown) from the master blood bag 73 through a liquid transfer port 74.
FIG. 2B illustrates the condition of the master blood bag at an above-mentioned stage of transfer.
Then, the plasma component still remaining in the master bag 73, the buffy coat and a part of the erythrocytes component are transferred into a second sub-bag (not shown) through repetitions of the procedure similar to the above.
FIG. 2C represents a post-transfer condition of the master blood bag 73 after the transfer of blood components has been completed.
In the prior art, the transfer of blood components is carried out in the above-described manner, from the master blood bag in which the whole blood is first gathered, into respective sub-bags.
However, it must be noted that the prior art wherein said separator 71 is used for the transfer of blood components is confronted with such a problem giving rise to an inconvenience that the leukocytes and platelets which are respective components constituting the buffy coat, get into each liquid drain port 91 provided at the upper portion of the master bag 73 by accident.
Normally, these blood components must be transferred into the second sub-bag.
Such an inconvenience would result in that the dense erythrocytes left as the lowermost layer in the master blood bag 73, which is due to be recovered, would sometimes undergo accidental mixing with the leukocytes and platelets, with a consequential problem thereby caused, entailing an inconvenience that there would be insufficiency of removing the leukocytes, etc. from the dense erythrocytes. Further, when the platelets are recovered from the buffy coat previously transferred into the second sub-bag, it gives rise to another problem of being a low recovery with the platelets because a part of the buffy coat remains in the master bag 73.
In order to solve these problems, it has been proposed that, as shown in FIG. 3, a shoulder part 93 of the master blood bag 73 be so formed with an acute angle of .theta. defined as being approximately 18.degree. against the horizontal line, whereby a downward shoulder line might be provided, thereby increasing the flow rate of each blood component running through the liquid transfer port 74 so that no buffy coat would flow into each liquid drain port 91. Regrettably, however, such a proposal failed to sufficiently eliminate the problems mentioned above.